Among the difficulties encountered when attempting to perform a fabrication process (such as deposition or etch) on a semiconductor wafer is the difficulty of maintaining maximum process uniformity within the wafer. Most semiconductor fabrication processes, including etch and deposition processes, are activated thermally or via mass transport (or their combination). Thus, good process uniformity usually requires adjustments and optimizations of both the wafer temperature uniformity and gas flow pattern. Advanced semiconductor process equipment employ multizone resistive, induction, or lamp-type heat sources to optimize the temperature uniformity within the wafer in order to establish improved process uniformity.
The process uniformity may be also affected by the ability to distribute the process gases according to a desired flow pattern. For the most part, the efforts to alleviate the problems caused by the gas flow patterns and mass transport nonuniformity in the process chamber to establish uniform processes have been in the direction of maintaining absolute uniformity of thickness of the material being deposited or etched. However, since the process uniformity usually depends upon both uniformity temperature within the wafer and mass transport uniformity of the process gases, some applications have relied on adjusting the wafer temperature distribution (which can usually be controlled) in order to compensate for nonuniform mass transport effects.
As an example of the above, in the chemical-vapor deposition (CVD) of tungsten, the deposition uniformity is strongly affected by gas flow patterns as well as the wafer temperature distribution. It is possible to improve the tungsten thickness uniformity by adjusting the wafer temperature distribution. The optimum deposition (thickness) uniformity may require a non-uniform or intentionally distorted wafer temperature. A non-uniform wafer temperature may be required to minimize the undesirable affects of non-uniform reactant concentration or mass transport distribution as well as to eliminate the gas or reactant depletion effects. A distorted non-uniform wafer temperature may overcome the flow non-uniformity effects resulting in a relatively uniform layer thickness. However, an intentionally distorted wafer temperature distribution can cause other problems, such as nonuniformities of other electrical and physical properties. As a result, intentional distortion of the wafer temperature in order to compensate for nonuniform mass transport effects may not be a desirable solution. Mechanical design constraints may contribute to the difficulty of maintaining the uniformity of gas flow from a single-zone gas injector. Accordingly, there is a need for the capability to allow real-time adjustments and control of the gas flow pattern and mass-transport distribution of reactants within the process chamber. This capability is useful in many fabrication processes such as plasma etch, thermal annealing/oxidation, depositions and other fabrication processes.